Halosilanes such as trichlorosilane and tetrachlorosilane are versatile compounds that are useful in a variety of applications such as for production of polycrystalline silicon. Polycrystalline silicon is a vital raw material used to produce many commercial products including, for example, integrated circuits and photovoltaic (i.e., solar) cells. Polycrystalline silicon is often produced by a chemical vapor deposition mechanism in which silicon is deposited from silane or a halosilane onto silicon particles in a fluidized bed reactor or onto silicon rods as in a Siemens-type reactor. The seed particles continuously grow in size until they exit the reactor as polycrystalline silicon product (i.e., “granular” polycrystalline silicon).
To produce electronic grade polycrystalline silicon which is used in semiconductor and solar industries, the silane or halosilane deposition gases must be relatively free of contaminants often found in such gases such as arsenic and phosphorous impurities. Conventional methods for removing such impurities involve additives that are used to complex phosphorous and/or arsenic followed by removal of the complexed compounds. It has been reported that the compounds may be removed by distillation in a column with a relatively high reflux ratio and/or a relatively high number of theoretical stages (or even by use of two columns operated in series), which causes the distillation operation to not be cost effective relative to other methods.
A continuing need exists for methods for purifying halosilane process streams and, in particular, for methods that remove arsenic and phosphorous from such process streams.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.